Human societies may be modeled as very large complex systems involving multiple flows of energy and materials between different sectors. Traditional exergy analysis methods are inadequate for the analysis of such systems because they do not take non-energetic flows into account. Extended exergy analysis (EEA) allows for the inclusion of exergetic equivalents of such non-energetic quantities as labor, capital and the costs of environmental remediation. The economy is divided into seven sectors reflecting the organization of economic data reported by Statistics Canada. A model of the structural connectivity of the economy in terms of exchanges between sectors is constructed using economic data generated by Statistic Canada. Energy, exergy, and extended exergy efficiencies are calculated for each sector of the economy of Nova Scotia and compared with those of Norway, China, Italy, and the UK to identify similarities and differences between the composition and performance of sectors around the world.

The concept of exergy is defined and applied to district heating systems. The influence from different reference state conditions and system boundaries are explained in some detail. The aim is to show the simplicity and value of using the concept of exergy when analyzing district heating processes. The exergy factor is introduced and applied for a number of Swedish and Danish district heating systems. This varies from 14.2% to 22.5% for Swedish district heating systems. The higher the exergy factor, the more the exergy losses in the passive conversion towards space heating. Large losses revealed in an exergy treatment of a process should be seen as a challenge to achieve technical improvements of the system.

Natural gas has been considered a clean energy which is more environmental friendly and with higher combustion efficiency. In Taiwan, most LNG was imported from abroad, with large amount of cold energy for application, despite the fact that it has been utilized for only 8% of total. In LNG cold energy utilization process, the change of exergy can be simulated with the second law of Thermodynamics as a means to analyze its energy efficiency. Especially, when the transportation distance is long, the optimal insulation thickness can then be calculated to justify its economic feasibility. In this study, thermoeconomics was applied to analyze the feasibility of LNG cold energy recovery, which warrants it as a powerful design tool in engineering applications.

This research work presents the thermodynamic analysis of hydrogen production using steam methane reforming process at different conditions. The model is developed using HSC 4.1 software and spreadsheet. Methane is chosen to represent the carbonaceous fuel and steam methane reforming process (once through and cyclic) for hydrogen production is analyzed based on 1st law and 2nd law of thermodynamics i.e., energetic and exergetic efficiencies. The mass, energy and exergy analysis of each step is done. The optimal condition for production of maximum hydrogen is found using CO2 removal agent and O2 transfer compound. The efficiency is calculated as a function of steam content, temperature and amount of CO2 removal agent and O2 transfer compound. The pressure is kept constant at one atmosphere. Operating temperature, CaO loading, Fe2O3 loading and H2O content is determined from the once through process. It is found that the maximum H2 production is with the cyclic process. Maximum H2 produced in cyclic process with CaO & Fe2O3 loadings is 99.2%. Also CO2 content is comparatively lower in cyclic process. Theoretical efficiencies can be used to compare with the available data which will help to minimize the losses in the process. The results can be used as a baseline for the design of H2 production technology. The main aim of this research is to develop a thermodynamic protocol for evaluating hydrogen production processes.

Though the field of hypersonic vehicle design is thriving again, few studies to date demonstrate the technology through a mission in which multiple flight conditions and constraints are encountered. This is likely due to the highly integrated and sensitive nature of hypersonic vehicle components. Consequently, a formal Mach 6 through Mach 10 flight envelope is explored which includes cruise, acceleration/climb, deceleration/descend and turn mission segments. An exergy approach to the vehicle synthesis/design, in which trade-offs between dissimilar technologies are observed, is proposed and measured against traditional methods of assessing highly integrated systems. A quasi one-dimensional hypersonic vehicle system simulation program was constructed. Composed of two sub-systems, propulsion and airframe, mechanisms for loss are computed from such irreversible processes as shocks, friction, heat transfer, mixing, and incomplete combustion. The propulsion sub-system consists of inlet, combustor, and nozzle, while the airframe provides trim and force accounting measures. An energy addition mechanism, based on the potential of MHD technology, is utilized to maintain a shock-on-lip inlet operating condition. Thirteen decision variables (seven design and six operational) were chosen to govern the vehicle geometry and performance. A genetic algorithm was used to evaluate the optimal vehicle synthesis/design for three separate objective functions, i.e the optimizations involved the maximization of thrust efficiency, the minimization of fuel mass consumption, and the minimization of exergy destruction plus fuel exergy loss. The principal results found the minimum fuel consumption and minimum exergy destruction measures equivalent, both meeting the constraints of the mission while using 11% less fuel than the thrust efficiency measure. Optimizing the vehicle for the single most constrained mission segment yielded a vehicle capable of flying the entire mission but with fuel consumption and exergy destruction plus fuel loss values greater than the above mentioned integrated vehicle solutions. In essence, the mission-level analysis provided much insight into the dynamics of mission-level hypersonic flight and demonstrated the usefulness of an exergy destruction minimization measure for highly integrated synthesis/design. / Master of Science

This thesis work presents detailed results of the application of exergy-based methods to highly dynamic, integrated aerospace systems such as hypersonic vehicle concepts. In particular, an exergy-based methodology is compared to a more traditional based measure by applying both to the synthesis/design and operational optimization of a hypersonic vehicle configuration comprised of an airframe sub-system and a propulsion sub-system consisting of inlet, combustor, and nozzle components. A number of key design and operational decision variables are identified as those which govern the hypersonic vehicle flow physics and thermodynamics and detailed one-dimensional models of each component and sub-system are developed. Rates of exergy loss as well as exergy destruction resulting from irreversible loss mechanisms are determined in each of the hypersonic vehicle sub-systems and their respective components. Multiple optimizations are performed for both the propulsion sub-system only and for the entire hypersonic vehicle system for single mission segments and for a partial, three-segment mission. Three different objective functions are utilized in these optimizations with the specific goal of comparing exergy methods to a standard vehicle performance measure, namely, the vehicle overall efficiency. Results of these optimizations show that the exergy method presented here performs well when compared to the standard performance measure and, in a number of cases, leads to more optimal syntheses/designs in terms of the fuel mass flow rate required for a given task (e.g., for a fixed-thrust requirement or a given mission). In addition to the various vehicle design optimizations, operational optimizations are conducted to examine the advantage if any of energy exchange to maintain shock-on-lip for both design and off-design conditions. Parametric studies of the hypersonic vehicle sub-systems and components are also conducted and provide further insights into the impacts that the design and operational decision variables and flow properties have on the rates of exergy destruction. / Master of Science

This thesis work shows the advantages of applying exergy-based analysis and optimization methods to the synthesis/design and operation an Advanced Aircraft Fighter (AAF) with three subsystems: a Propulsion Subsystem (PS), an Environmental Control Subsystem (ECS), and an Airframe Subsys-tem - Aerodyanmics (AFS-A) is used to illustrate these advantages. Thermodynamic (both energy and exergy), aerodynamic, geometric, and physical models of the components comprising the subsystems are developed and their interactions defined. An exergy-based parametric study of the PS and its components is first performed in order to show the type of detailed information on internal system losses. This is followed by a series of constrained, system synthesis/design optimizations based on five different objective functions, which define energy-based and exergy-based measures of performance. A first set of optimizations involving four of the objectives (two energy-based and two exergy-based) are performed with only PS and ECS degrees of freedom. Losses for the AFS-A are not incorporated into the two exergy-based objectives. The results show that as expected all four objectives globally produce the same optimum vehicle.A second set of optimizations is then performed with AFS-A degrees of freedom and again with two energy- and exergy-based objectives. However, this time one of the exergy-based objectives incorporates AFS-A losses directly into the objective. The results are that this latter objective produces a significantly better optimum vehicle. Thus, an exergy-based approach is not only able to pinpoint where the greatest inefficiencies in the system occur but produces a superior optimum vehicle as well by accounting for irreversibility losses in subsystems (e.g., the AFS-A) only indirectly tied to fuel usage. / Master of Science

Yes / The reverse osmosis (RO) process is one of the most popular membrane technologies for the generation of freshwater from seawater and brackish water resources. An industrial scale RO desalination consumes a considerable amount of energy due to the exergy destruction in several units of the process. To mitigate these limitations, several colleagues focused on delivering feasible options to resolve these issues. Most importantly, the intention was to specify the most units responsible for dissipating energy. However, in the literature, no research has been done on the analysis of exergy losses and thermodynamic limitations of the RO system of the Arab Potash Company (APC). Specifically, the RO system of the APC is designed as a medium-sized, multistage, multi pass spiral wound brackish water RO desalination plant with a capacity of 1200 m3/day. Therefore, this paper intends to fill this gap and critically investigate the distribution of exergy destruction by incorporating both physical and chemical exergies of several units and compartments of the RO system. To carry out this study, a sub-model of exergy analysis was collected from the open literature and embedded into the original RO model developed by the authors of this study. The simulation results explored the most sections that cause the highest energy destruction. Specifically, it is confirmed that the major exergy destruction happens in the product stream with 95.8% of the total exergy input. However, the lowest exergy destruction happens in the mixing location of permeate of the first pass of RO desalination system with 62.28% of the total exergy input.

Heat sources such as biomass, industrial waste heat and solar thermal provide the potential to produce renewable environmentally low impact electricity. Using these resources efficiently within economic constraints is important for viability of these systems. This thesis explores a regenerative organic Rankine cycle for use in low temperature heat sources. A Bitzer model scroll expander is used for the prime mover for the system. This expander has a reliable model in which thermodynamic analysis can be done. Various working fluids are explored to investigate which one will provide the most power output and efficiency within system constraints. Using optimization, each fluid is tested within physical constraints for optimal operating conditions using system exergy efficiency as the objective function. An exergoeconomic analysis is performed to predict the cost rate of electricity of the system and is compared to current contract rates from the Ontario Power Authority. Dimethyl ether shows promising results with a system exergy efficiency of 11.76% and system energy efficiency of 2.84% at a source temperature of 120℃. The degree of superheat and pressure ratio are used as the independent variables in the optimization. Highest isentropic efficiency for the expander is 29.22%, showing large potential for improvement. Electricity cost rates for the system assuming 20 year life are 0.132 $/kWh to 0.197 $/kWh depending on the fuel input cost for dimethyl ether. At the current state the system shows merit with large potential for improvement in the expander. / UOIT

A solar based integrated system for hydrogen and methanol production is investigated. Energy and exergy analyses of a hydrogen production plant, thermodynamic assessment of methanol synthesis plant, and exergy analysis of the integrated solar based system for hydrogen and methanol production are performed. The analysis of hydrogen production is found to be essential in order to investigate for further design parameters for methanol synthesis procedure. The present analysis shows the effects of temperature and current density on hydrogen production. Thermodynamic parameters of the methanol synthesis plant, such as temperature and pressure, appear to be an important role in methanol production. Based on the methods of physical domain of the system, the optimum temperature of methanol synthesis is obtained for the final design of the methanol plant. It is concluded that increasing pressure improves the methanol synthesis process; however, methanol conversion takes place at 493 K. The energy and exergy efficiencies of the system are reduced by 30% if the electrolyser operates at 300 K. The efficiencies of the system are also highly dependent on the solar intensity. The system efficiencies can be tripled if the intensity of solar radiation is increased to 600 W/m2 instead of 250 W/m2. / UOIT